Does anybody help me with my issue: how to do this this effect with menu on this site  http://qazxsw-ru.1gb.ru/  All what I have at this moment is  http://jsfiddle.net/BrZaa/2/

My goal is: 

1. My draggable element mustn't left area of container 

2. And when it's start dragging from green to blue area then border of my dragging element must be concur with borders of blue element

P.S.: I'm new in JQuery, maybe I'm using wrong technique?